JP2015001140A - Excavation method, construction method for underground structure, wall body member, and wall body for excavation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excavation method and the like, which enable efficient execution of ground excavation work.SOLUTION: After a cylindrical cut-off wall 10 reaching an impermeable stratum is constructed in ground 1, a wall body 20 for excavation, in which a wall body member 21 is assembled in a cylindrical shape, is lowered inside the cut-off wall 10 depending on the excavation of the ground 1 inside the cut-off wall 10. Thus, the ground 1 is excavated. A structure 30 is constructed in an excavation location 1b where the excavation is performed in this way. Subsequently, the wall body 20 for the excavation is sequentially dismantled from a lower end, and the periphery of the structure 30 is backfilled while the individual wall body member 21 is recovered.

Description

  The present invention relates to an excavation method for excavating the ground, an underground structure construction method for excavating the ground and constructing a structure at the excavation site, and an excavation wall body and a wall body for forming the excavation wall body. It relates to members.

  In order to construct structures such as frame foundations, construction to excavate permeable ground may be performed. In such a case, a temporary steel sheet pile is driven around the excavation site to the impermeable layer of the ground, and the inside is often excavated by using it as a water stop wall and a mountain stop.

  As a normal method, every time the inside of the steel sheet pile is excavated to a predetermined depth, a ring-shaped stile beam made of reinforced concrete is installed as a support material along the inner circumference of the steel sheet pile on the side of the excavation site. There is a method of excavation by repeating.

  When the excavation is completed, a structure is constructed at the excavation site, and the supporting materials are removed in order from the bottom while refilling the periphery of the structure. In addition, as a support material, an earth anchor may be provided from the inside of the steel sheet pile to the surrounding ground, and a receiving beam for the earth anchor may be installed inside the steel sheet pile.

  Similarly, as a method of excavating the inner side while supporting the surrounding ground, in recent years, a method of underwater excavation while pressing the wall 100 for excavation into the ground 1 as shown in FIG. (See Patent Documents 1 to 4). This wall for excavation 100 is formed by assembling a wall member 101, which is a segment made of steel or reinforced concrete, into a cylindrical shape, and a blade fitting 102 is provided at the lower end.

  In such a case, when excavation is completed, as shown in FIG. 12 (b), underwater concrete 103 is placed on the bottom of the excavation, and then the inside of the excavation wall 100 is drained to construct a structure. Backfill the surrounding area. The placement of the underwater concrete 103 is performed to prevent intrusion of groundwater into the inside of the wall 100 for excavation during drainage and to stabilize the surrounding ground.

Japanese Patent No. 3453664 Japanese Patent No. 2,681,741 Japanese Patent Laid-Open No. 2004-332202 JP 2008-125555 A

  In the general method of excavating inside the steel sheet pile, there is a problem that the installation and removal work of the support material is complicated and troublesome. In addition, the safety is low and work efficiency is poor because excavation of the ground, installation of support materials, construction of structures, removal of support materials, backfilling of the ground and work types are replaced.

  Furthermore, when a reinforced concrete stile beam is used as the support material, the next excavation will not take place until the strength of the stile beam is developed, so the overall construction period will be longer. It is also difficult to remove, and often leaves stile beams and steel sheet piles, which wastes resources. In addition, since the stile beam becomes large, it is necessary to excavate the inside with a steel sheet pile surrounding a range having a sufficient margin with respect to the size of the structure so as not to interfere with the stile beam during construction of the structure. As a result, the number of steel sheet piles will increase, the amount of excavated soil and the amount of backfilled soil will increase. An H-section steel or the like is also used as the stile beam, but there is a similar problem in this case.

  Even when an earth anchor or the like is used as a support material, it is necessary to put a boring machine inside the steel sheet pile for anchor installation, and the work becomes difficult unless the space inside the steel sheet pile is large. In addition, excavators and boring machines are frequently put in and out, and workability is poor. Furthermore, it is difficult to manage the tension of the anchor, and if too much tension is applied, the outward force acting on the steel sheet pile will increase, causing the steel sheet pile to open and water leakage may occur. Moreover, since it removes after construction of a structure, it is necessary to set it as an expensive removal type anchor, and cost increases. Furthermore, when the excavation site is close to the site boundary, the end of the anchor goes out of the site and may not be adopted.

  On the other hand, in the method using the excavation wall as described above, the supporting material can be omitted, but the work is complicated because the ground is excavated underwater. In addition, after excavating under the cutting edge of the wall for excavation, it is press-fitted, so that the surrounding ground is easily deformed. Moreover, since it becomes underwater excavation, a weak layer and unevenness are likely to remain on the bottom surface of the excavation, and underwater concrete has to be thickened to 3 to 4 m to cope with an uplift during drainage, and the cost is high. Furthermore, since there is a permeable ground containing groundwater outside the wall for excavation, it is difficult to remove the wall for excavation in parallel with the backfilling work due to the fear of inflow of groundwater. Further, since the lower end of the wall and the underwater concrete are bonded, it is difficult to pull up after the backfilling is completed. As a result, there are many cases where they are buried and waste is increased. The excavated soil contains water, and if it is not dried, it becomes construction sludge, and construction costs are also incurred.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an excavation method and the like capable of efficiently excavating the ground.

  According to a first aspect of the present invention for achieving the above object, a wall member is provided in accordance with a step of constructing a cylindrical water blocking wall reaching the impermeable layer on the ground, and excavation of the ground inside the water blocking wall. And a step of lowering a wall for excavation assembled in a cylindrical shape inside the water blocking wall.

  In the present invention, after the water blocking wall is constructed, the ground is excavated on the inside, and the wall for excavation in which the wall member is assembled into a cylindrical shape is lowered, so that the work becomes easy in the air and the work is easy as described above. There is no problem. Furthermore, since the pressure (earth pressure, water pressure) of the surrounding ground applied to the water blocking wall can be finally supported by the wall for excavation, it is not necessary to separately provide a reinforcing material on the water blocking wall and work efficiency is good. Moreover, since the wall for excavation is inside the water blocking wall, there is no influence of groundwater upon removal, and it can be easily removed after construction of the structure or after backfilling. The wall member recovered by removing the wall for excavation can be diverted to other works, and is excellent in terms of cost. Furthermore, since the wall for excavation is formed in a cylindrical shape, strength can be ensured even if it is thin, and since it can be shaped along the water blocking wall, the space occupied in the inner space of the water blocking wall is small compared to stile beams, There is little risk of interference when constructing structures. As a result, the size of the inner space of the water blocking wall can be made closer to the size of the structure, and the cost for construction of the water blocking wall, the amount of excavated soil and the amount of backfilled soil can be minimized. .

It is desirable to alternately perform excavation of the ground inside the water blocking wall and lowering of the excavation wall body inside the water blocking wall.
Thus, excavation work can be facilitated by excavating in order.

It is preferable that a spacer is provided on the outer surface of the wall member.
Accordingly, it is easy to reduce the deformation of the water blocking wall, and the wall for excavation can be accurately lowered along the water blocking wall. The spacer also has a role of transmitting pressure from the surrounding ground to the wall for excavation by contacting the water blocking wall.

It is preferable that the wall member is provided with a stopper that interferes with the water blocking wall in a plane when the excavation wall body is lowered.
Thereby, it is possible to prevent the oversinking by controlling the descending width of the wall for excavation.

First, it is desirable to excavate the ground at least at a portion inside the water blocking wall along the circumferential direction of the excavation wall, and then lower the excavation wall.
Accordingly, a force applied when the excavation wall body is lowered is small, and it is easy to maintain the horizontal posture of the excavation wall body.

The wall for excavation is preferably lowered by press-fitting using a jack. Moreover, it is desirable to bear the reaction force at the time of press-fitting on the water blocking wall.
As a result, the wall for excavation can be easily lowered, and the jack can be operated on the ground, so that workability is high.

It is also desirable that the excavation wall be lowered by placing a heavy object and press-fitting it.
This is also preferable because the same effect as described above can be obtained.

  The second invention includes a step of constructing a cylindrical water blocking wall reaching the water-impermeable layer on the ground, excavation of the ground inside the water blocking wall, and adding a wall member to the lower side to assemble the tube into a cylindrical shape. And a step of alternately performing the construction of the wall for excavation inside the water blocking wall.

  This also provides the same effects as described above, such as excavation work for the ground and removal of the wall for excavation. Further, the excavation wall body can also have a simple configuration, and jacking work for lowering the excavation wall body is not necessary.

The third invention is for excavation in which a wall member is assembled into a tubular shape in accordance with a step of constructing a cylindrical water blocking wall reaching the impermeable layer on the ground and excavation of the ground inside the water blocking wall. A step of lowering a wall body inside the water blocking wall, a step of constructing a structure at an excavation site, and a step of backfilling the periphery of the structure and removing the wall for excavation. It is an underground structure construction method characterized by
Moreover, it is desirable to alternately perform excavation of the ground inside the water blocking wall and lowering of the excavation wall body inside the water blocking wall.

  In a fourth aspect of the present invention, a cylindrical water blocking wall reaching the impermeable layer is constructed on the ground, the ground inside the water blocking wall is excavated, and the wall member is added to the lower side to assemble the cylinder. The step of alternately constructing the excavation wall body inside the water blocking wall, the step of constructing the structure at the excavation site, the backfilling of the periphery of the structure, and the excavation wall body A method of constructing an underground structure characterized by comprising:

5th invention is for assembling the cylindrical excavation wall body arrange | positioned inside the said water stop wall when excavating the inner side of the cylindrical water stop wall which reaches the impermeable layer built in the ground It is a wall member, Comprising: A spacer is provided in an outer surface, It is a wall member characterized by the above-mentioned.
The wall for excavation is lowered inside the water blocking wall, and the wall member is provided with a stopper that interferes with the water blocking wall in a plane when the wall for excavation is lowered. desirable.

The sixth invention is formed by assembling a wall member into a cylindrical shape, which is disposed inside the water blocking wall when excavating the inside of the cylindrical water blocking wall reaching the impermeable layer built on the ground. The excavation wall body is characterized in that a spacer is provided on the outer surface of the wall member.
Preferably, the excavation wall body is lowered inside the water blocking wall, and the wall body member is provided with a stopper that interferes with the water blocking wall in a plane when the excavation wall body is lowered. .

  ADVANTAGE OF THE INVENTION According to this invention, the excavation method etc. which can perform excavation work of a ground efficiently can be provided.

The figure which shows the middle of excavating ground 1 The figure which shows bracket 23 vicinity The figure which shows the detail of the wall 20 for excavation The figure which shows excavation of the ground 1 using the wall body 20 for excavation The figure which shows excavation of the ground 1 using the wall body 20 for excavation The figure shown about the descent | fall of the wall 20 for excavation The figure which shows excavation of the ground 1 using the wall body 20 for excavation Diagram showing construction of structure 30 The figure which shows removal of the wall 20 for excavation The figure which shows excavation of the ground 1 using the wall body 20 for excavation The figure which shows excavation of the ground 1 using the wall body 20 for excavation Diagram showing conventional excavation method

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
(1. Water blocking wall and excavation wall)
FIG. 1 is a view showing a state where the ground 1 is being excavated by the excavation method according to the first embodiment of the present invention. FIG. 1A is a view of the vertical direction, and FIG. 1B is a view of FIG. 1A viewed from above.

  As shown in FIGS. 1A and 1B, in this embodiment, when excavating the water permeable layer 1 a of the ground 1, a water blocking wall 10 that reaches the water impermeable layer 1 a ′ is constructed in the ground 1, and the water blocking wall is formed. The excavation wall 20 is lowered in accordance with the excavation inside 10.

  The water blocking wall 10 has a circular plane and is placed so that the lower end reaches the impermeable layer 1a 'below the permeable layer 1a. The water blocking wall 10 is arranged in a circular shape by alternately arranging the steel sheet piles 10a and 10b having a substantially U-shaped plane, with the depression direction being different between the inside and outside of the steel sheet piles 10a and 10b. Arranged and configured.

  The excavation wall 20 is a cylindrical body having a circular plane, and is arranged around the excavation site 1 b along the inner side of the water blocking wall 10. The wall 20 for excavation is formed by connecting the wall members 21 with bolts or the like and assembling them into a cylindrical shape.

  At the lower end of the excavation wall 20, a blade base 22 having a sharp tip is provided. A bracket 23 is attached to the wall member 21 at the upper end portion of the wall 20 for excavation in the ground portion. The wall 20 for excavation is press-fitted and lowered into the ground 1 using the jack 11 arranged on the bracket 23. In the present embodiment, as shown in FIG. 1B, four brackets 23 and jacks 11 are arranged at equal intervals in the circumferential direction. However, the arrangement is not limited to this, and the posture of the wall 20 for excavation is determined. Anything that can be kept horizontal and descend can be used.

  FIG. 2 is a view showing the vicinity of the bracket 23. The wall 20 for excavation is lowered using the jack 11 disposed on the bracket 23. As the jack 11, for example, a center hole jack through which a PC steel material 213 is inserted is used. The lower end of the PC steel 213 is attached to the upper end of the water blocking wall 10, and when the wall for excavation 20 is press-fitted by the jack 11, the reaction force is borne by the water blocking wall 10.

  In the wall member 21 at the upper end of the excavation wall 20 in the ground portion, a stopper 212 is attached to the outer surface below the bracket 23. The stopper 212 is provided so as to interfere with the water blocking wall 10 in a plane when the excavation wall body 20 is lowered, and prevents the excavation wall body 20 from being oversunk by contacting the water blocking wall 10.

  FIG. 3 is a view showing details of the wall 20 for excavation. FIG. 3A is a perspective view showing an upper end portion of the wall 20 for excavation, and shows a state before the bracket 23 and the stopper 212 are attached. FIG. 3B is a plan view showing a part of the circumferential direction of the wall 20 for excavation, and FIG. 3C is a sectional view in the vertical direction along the line AA in FIG.

  As shown in FIG. 3A, the wall member 21 is a segment made of steel or reinforced concrete having an arcuate plane. The wall 20 for excavation is formed by connecting wall members 21 vertically and horizontally with bolts or the like.

  A spacer 211 is provided on the outer surface of the wall member 21 so as to protrude outward. As shown in FIG. 3 (b), the spacer 211 is located at a position corresponding to the steel sheet pile 10 a arranged with the depression direction as the inner side, and the innermost side of the water blocking wall 10 and the outer side surface of the excavation wall body 20. Hold the interval. Thereby, the deformation of the water blocking wall 10 is prevented, and the excavation wall 20 can be accurately lowered along the water blocking wall 10. The shape, size, arrangement, and the like of the spacer 211 may be determined so that the interval between the water blocking wall 10 and the excavation wall body 20 can be appropriately maintained, and is not limited to that illustrated. For example, the spacer 211 may be provided only on some of the wall members 21.

(2. Excavation of ground 1 and construction of structure, removal of wall 20 for excavation)
In this embodiment, after excavating the ground 1 using the above-described excavation wall body 20, a structure is constructed at the excavation site and the excavation wall body 20 is removed. This procedure will be described below.

  In the present embodiment, first, steel sheet piles 10a and 10b (see FIG. 1B) are placed around the excavation site as described above, and the lower end portion is impermeable layer 1a as shown in FIG. 4A. Build a water blocking wall 10 that reaches'.

  And as shown in FIG.4 (b), it excavated by predetermined depth (for example, about 1 m) equally in the substantially whole area inside the water stop wall 10 with an excavator, and the wall body member 21 was assembled and formed in the cylinder shape. The wall 20 for excavation is arrange | positioned in the excavation location 1b. The excavation wall body 20 is arranged along the inner periphery of the water blocking wall 10 slightly inside the water blocking wall 10, and a blade fitting 22 is provided at the lower end. Further, the bracket 23 and the stopper 212 (see FIG. 2) are attached to the wall member 21 at the upper end of the excavation wall 20 in the ground portion, and the jack 11 is disposed on the bracket 23.

  Next, as shown in FIG. 5 (a), the inside of the water blocking wall 10 is excavated uniformly at a predetermined depth (for example, about 1 m) in almost the entire region including the portion corresponding to the circumferential direction of the excavation wall body 20. To do. Here, only the ground 1 at the inner peripheral edge of the water blocking wall 10 is left so that the excavation wall 20 can be supported at a minimum by contacting the tip of the blade fitting 22. However, for example, when the spacer 211 is in contact with the water blocking wall 10 and the wall 20 for excavation can be supported by the frictional force, the inner peripheral edge of the water blocking wall 10 may also be excavated.

  Further, the excavation of the ground 1 is performed while the groundwater level is lowered by appropriately pumping the groundwater of the ground 1 inside the water blocking wall 10 by a pump (not shown) or the like. In the present embodiment, since the water blocking wall 10 reaching the impermeable layer 1a 'is constructed, the groundwater does not flow from the surroundings even if the groundwater level is lowered as described above.

  When the ground 1 is excavated as shown in FIG. 5A, next, the jack 11 is used to apply pressure almost evenly in the circumferential direction of the excavation wall body 20 while maintaining the horizontal posture. As shown in FIG. 5B, press-fitting is performed at a predetermined depth (for example, about 1 m). At this time, since the resistance from the ground 1 is only received from the ground 1 left on the inner peripheral edge of the water blocking wall 10, the force applied when the jack 11 is press-fitted is small.

  The excavation wall body 20 is press-fitted while controlling the press-fitting width. However, even if a mistake occurs, the stopper 212 abuts on the upper end of the water blocking wall 10 as shown in FIG. Thus, the oversinking of the excavation wall body 20 is prevented.

  After the excavation wall 20 is lowered, the wall member 21 assembled in a ring shape is added to the upper end of the excavation wall 20, as shown in FIG. Then, as shown in FIG. 6C, the bracket 23 and the stopper 212 are rearranged on the wall member 21 at the upper end portion in the ground portion, and the jack 11 is moved and disposed on the bracket 23.

  FIG. 7A shows a state where the above operations are performed. Thereafter, the operations described in FIGS. 5A, 5B, 6B, and 6C are repeated in order, and the excavation wall body 20 is lowered according to excavation of the ground 1. The excavation is continued in this manner, and the lower end of the excavation wall 20 is lowered to a position slightly shallower than the final excavation depth (for example, a position shallower by about 1.5 to 2 m) as shown in FIG. Let

  Then, as shown to Fig.8 (a), it excavates to the final excavation depth, leaving the inner peripheral edge part of the water stop wall 10 which contact | connects the front-end | tip of the blade tip metal fitting 22. FIG. When the ground 1 is excavated in this way, as shown in FIG. 8B, a structure 30 is constructed at the excavation location 1b. In the present embodiment, the housing base is formed as the structure 30, but the structure 30 is not limited to this.

  Thereafter, as shown in FIG. 9A, the excavation wall body 20 is sequentially disassembled from the lower end portion to collect individual wall body members 21 and the like, and the excavation site 1b around the structure 30 is excavated soil or the like. Backfill with. The jack 11 and the bracket 23 are also disassembled at this time. If necessary, the upper end portion of the excavation wall body 20 can be attached and fixed to the water blocking wall 10 to prevent the excavation wall body 20 from sinking due to the dismantling of the lower end portion of the excavation wall body 20. .

  9B, when the excavation wall 20 is removed by refilling the periphery of the structure 30 to the ground surface, the steel sheet piles 10a and 10b of the water blocking wall 10 are finally obtained (see FIG. 1B and the like). ) Is removed and removed. The structure 30 is constructed as described above.

  As described above, according to the present embodiment, after the water blocking wall 10 reaching the impermeable layer 1a ′ is constructed, the ground 1 is excavated on the inside thereof, and the wall member 21 is assembled in a cylindrical shape. Since the wall body 20 is lowered, it becomes excavation in the air and work can be performed easily. For example, unlike underwater excavation described above, there is no need to press-fit after excavating the blade edge of the wall 20 for excavation, and there is no possibility of deforming the surrounding ground. Moreover, it is not necessary to place underwater concrete and the cost can be reduced, and it is not necessary to excavate extra in consideration of the thickness of the placement. Furthermore, since a person enters the excavation site 1b, during final excavation, excavation can be performed so that the ground of the excavation bottom surface part for constructing the structure 30 is scraped while visually observing the structure 30. The support ground will not be damaged. It is also possible to confirm the ground support force when the structure 30 is constructed. Moreover, since excavated soil is not exposed to groundwater, it can be treated as construction residual soil.

  Furthermore, since the pressure (earth pressure, water pressure) of the surrounding ground applied to the water blocking wall 10 can be finally supported by the wall 20 for excavation, it is not necessary to separately provide a reinforcing material on the water blocking wall 10 and work efficiency is also improved. good. In addition, since the excavation wall 20 is inside the water blocking wall, there is no influence of the surrounding ground water upon removal, and it can be easily removed after the structure 30 is constructed. The wall member 21 recovered by removing the wall 20 for excavation can be diverted to other works, and is excellent in terms of cost. Furthermore, since the wall 20 for excavation is formed in a cylindrical shape, the strength can be ensured even if it is thin, and the shape can be formed along the inner periphery of the water blocking wall 10. The space occupied in the inner space is small, and there is little risk of interference when the structure 30 is constructed. As a result, the size of the inner space of the water blocking wall 10 can be made closer to the size of the structure 30, and the cost related to the construction of the water blocking wall 10, the amount of excavated soil and the amount of backfilled soil of the ground 1 can be reduced. Can be minimized.

  Further, in the present embodiment, the spacer 211 is provided on the outer surface of the wall member 21, so that it is easy to suppress the deformation of the water blocking wall 10, and the excavation wall body 20 is accurately moved along the water blocking wall 10. Can be lowered. The spacer 211 also has a role of transmitting pressure from the surrounding ground to the wall 20 for excavation by contacting the water blocking wall 10.

  In addition, since the wall member 21 is provided with a stopper 212 that interferes with the water blocking wall 10 in a plane when the digging wall body 20 is lowered, it is possible to control the descending width of the digging wall body 20 to prevent oversinking. Is possible.

  Further, in the present embodiment, after excavating the ground 1 in almost the entire inner side of the water blocking wall 10 including a portion along the circumferential direction of the excavation wall body 20, the excavation wall body 20 is lowered, Repeat alternately. Thus, excavation work can be facilitated by excavating in order. Further, since the resistance received from the ground 1 when the excavation wall body 20 is lowered is small, the force applied to the excavation wall body 20 can be small, and the horizontal orientation of the excavation wall body 20 can be easily maintained.

  However, the excavation procedure is not limited to this. For example, only a portion corresponding to the circumferential direction of the excavation wall body 20 may be excavated in advance, and the remaining portion (inside the excavation wall body 20) may be excavated after the excavation wall body 20 is lowered. Alternatively, the excavation wall 20 can be lowered as it is without excavating the portion corresponding to the circumferential direction of the excavation wall 20, and the ground 1 can be excavated inside. However, in this case, the resistance received from the ground 1 when the excavation wall 20 descends increases.

  In this embodiment, the wall 20 for excavation is press-fitted using the jack 11 and lowered, and the reaction force at the time of press-fitting is borne on the water blocking wall 10, so that the wall 20 for excavation can be easily lowered. It is possible to operate the jack 11 on the ground and the workability is high.

  However, when the wall 20 for excavation is press-fitted, a reaction force can be taken and press-fitted into an earth anchor or the like embedded in the ground 1. In addition, when the resistance force of the ground 1 or the frictional force of the spacer 211 between the water blocking wall 10 and the wall 20 for excavation is small, settlement due to its own weight is possible.

  In addition, as a method for press-fitting the excavation wall body 20, it is also possible to press-fit a heavy object placed on the excavation wall body 20 on the ground portion. In this case, the same effect as described above can be obtained. The shape and material of the heavy object are not particularly limited as long as the wall 20 for excavation can be press-fitted.

  Further, in this embodiment, the wall member 21 is sequentially disassembled and removed from the lower side of the excavating wall body 20, but the excavating wall body 20 is lifted upward while being backfilled and sequentially disassembled from the upper end. It is also possible to collect the wall member 21. Alternatively, after completion of backfilling, the excavation wall 20 can be pulled out and disassembled.

  Furthermore, in this embodiment, the water-stop wall 10 having a circular plane is constructed using the steel sheet piles 10a and 10b. However, the present invention is not limited to this, and the water-stop wall 10 having a rectangular shape can be constructed. It is also possible to use steel pipe sheet piles instead of the steel sheet piles 10a and 10b, or to construct the water blocking wall 10 by the SMW method (registered trademark) in which H-shaped steel is arranged as a core material in the soil mortar wall. It is.

  The shape of the wall 20 for excavation is not limited to a circular plane, but the plane may be rectangular, for example. The shape, material, and the like of the wall member 21 are not limited to those described above, and any material may be used as long as necessary strength can be obtained according to the shape of the wall 20 for excavation. For example, it is possible to use a high-strength segment with a large girder, or a segment with increased rigidity by using a beam or fire.

  Further, in this embodiment, the excavation wall body 20 is removed, but concrete is placed inside using the excavation wall body 20 as an outer mold, and the excavation wall body 20 is left to be a columnar or cylindrical shape. It is also possible to make structures.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 10 and FIG. 11 are diagrams for explaining the excavation method according to the second embodiment.

  The present embodiment is the same as the first embodiment in that the cylindrical water blocking wall 10 reaching the impermeable layer 1a ′ is constructed on the ground 1 and the wall 20 for excavation is disposed on the inside thereof. In accordance with excavation of the ground 1 inside the water blocking wall 10, the first embodiment is that the wall member 21 is added to the lower side and is assembled in a cylindrical shape so as to extend the excavation wall 20 downward. And different.

  That is, in the second embodiment, as shown in FIG. 10 (a), the water blocking wall 10 is constructed in the same manner as in the first embodiment, and the inside thereof is excavated to a predetermined depth. Is disposed at the excavation location 1b, and at this time, the upper end portion of the excavation wall body 20 is attached and fixed to the upper end portion of the water blocking wall 10 by the attachment portion 25.

  Then, after excavating the entire inner side of the water blocking wall 10 to a predetermined depth as shown in FIG. 10 (b), the wall member 21 is added to the lower side as shown in FIG. And the wall 20 for excavation is extended downward.

  Thereafter, the steps described in FIGS. 10B and 11A are repeated, and the excavation wall body 20 is constructed inside the water blocking wall 10 while excavating the ground 1 inside the water blocking wall 10 downward. I do. As shown in FIG. 11B, the above steps are performed until the lower end portion of the excavation wall body 20 comes to a position slightly shallower than the final excavation depth (for example, a position shallower by about 1.5 to 2 m). .

  The subsequent steps are the same as those in the first embodiment. That is, after excavating the ground 1 to the final excavation depth, a structure is constructed at the excavation location 1b. Thereafter, the excavation wall body 20 is sequentially disassembled from the lower end portion and the individual wall body members 21 are collected, and the excavation site 1b around the structure is backfilled with excavation soil or the like. When backfilling to the ground surface and removing the wall 20 for excavation, the water blocking wall 10 is finally removed.

  Even in the second embodiment, the same effects as those of the first embodiment can be obtained, such as excavation work of the ground 1 and removal of the wall 20 for excavation. Further, the wall 20 for excavation does not require the blade fitting 22 or the stopper 212 as in the first embodiment, and has a simple configuration. Further, jacking work for lowering the excavation wall 20 is not necessary.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, the technical scope of this invention is not influenced by embodiment mentioned above. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs.

1: ground 1a: permeable layer 1a ': impermeable layer 1b: excavation location 10: water blocking wall 11: jack 20: excavation wall 21: wall member 30: structure 211: spacer 212: stopper

Claims (16)

Constructing a cylindrical water blocking wall reaching the impermeable layer on the ground;
In response to excavation of the ground inside the water blocking wall, lowering the wall for excavation in which the wall member is assembled into a tubular shape inside the water blocking wall;
An excavation method comprising:   The excavation method according to claim 1, wherein excavation of the ground inside the water blocking wall and descent of the excavation wall body inside the water blocking wall are alternately performed.   The excavation method according to claim 1, wherein a spacer is provided on an outer surface of the wall member.   The excavation method according to any one of claims 1 to 3, wherein the wall member is provided with a stopper that interferes with the water blocking wall in a plane when the excavation wall body is lowered.   The excavation of the ground is first performed at least at a portion inside the water blocking wall along the circumferential direction of the excavation wall, and then the excavation wall is lowered. The excavation method according to claim 4.   The excavation method according to any one of claims 1 to 5, wherein the excavation wall body is lowered by being press-fitted using a jack.   The excavation method according to claim 6, wherein a reaction force when the jack is press-fitted is borne on the water blocking wall.   The excavation method according to any one of claims 1 to 5, wherein the excavation wall body is lowered by placing a heavy object and press-fitting. Constructing a cylindrical water blocking wall reaching the impermeable layer on the ground;
Alternately excavating the ground inside the water blocking wall and constructing a wall for excavation inside the water blocking wall by adding a wall member to the lower side and assembling into a tubular shape; and
An excavation method comprising: Constructing a cylindrical water blocking wall reaching the impermeable layer on the ground;
In response to excavation of the ground inside the water blocking wall, lowering the wall for excavation in which the wall member is assembled into a tubular shape inside the water blocking wall;
Building a structure at the excavation site;
Backfilling the periphery of the structure and removing the wall for excavation;
An underground structure construction method characterized by comprising:   The underground structure construction method according to claim 10, wherein excavation of the ground inside the water blocking wall and descent of the excavation wall body inside the water blocking wall are alternately performed. Constructing a cylindrical water blocking wall reaching the impermeable layer on the ground;
Alternately excavating the ground inside the water blocking wall and constructing a wall for excavation inside the water blocking wall by adding a wall member to the lower side and assembling into a tubular shape; and
Building a structure at the excavation site;
Backfilling the periphery of the structure and removing the wall for excavation;
An underground structure construction method characterized by comprising: A wall member for assembling a cylindrical wall for excavation arranged inside the water blocking wall when excavating the inner side of the cylindrical water blocking wall reaching the impermeable layer built on the ground, ,
A wall member characterized in that a spacer is provided on the outer surface. The excavation wall body is to be lowered inside the water blocking wall,
The wall member according to claim 13, wherein a stopper that interferes with the water blocking wall in a plane when the excavation wall is lowered is provided. A wall for excavation formed by assembling a wall body member into a cylindrical shape, which is arranged inside the water blocking wall when excavating the inner side of the cylindrical water blocking wall reaching the impermeable layer built on the ground Because
A wall for excavation, wherein a spacer is provided on an outer surface of the wall member. The excavation wall body is to be lowered inside the water blocking wall,
The wall member for excavation according to claim 15, wherein the wall member is provided with a stopper that interferes with the water blocking wall in a plane when the wall for excavation is lowered.

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